The present disclosure relates to the extraction and/or recovery of rare earth elements from coal ash, and systems and methods for doing so.
Rare earth elements (REEs) are a series of chemical elements found in the Earth's crust. REEs generally include elements 21, 39, and 57-71 on the periodic table. Due to their unique chemical properties, REEs have become critical in the development of many technologies spanning a range of applications including electronics, magnets, ceramics, computer and communication systems, transportation, health care, and national defense. The demand and cost of REEs has grown significantly over recent years, stimulating an emphasis on economically feasible approaches for REE recovery. Despite their criticality, however, there is currently not significant development of a domestic source of REEs.
Coal deposits in certain regions of the United States can be particularly rich in rare earth elements, on the order of about 1,000 parts-per-million (ppm). However, the combustion of coal in power stations for energy generation yields coal ash as its product. Coal ash may include fly ash and bottom ash from power generation stations, ash generated in a lower-temperature ashing process, and ash residual from a coal liquefaction process. The coal ash may contain REEs that are concentrated above 300 ppm, and the REEs could then be economically recovered. Processes for further concentrating and recovering REEs from coal ash would be desirable.